The control of loudness, pitch and quality in speech and voice requires coordination of all speech production systems, including the respiratory system, the larynx and the upper airways. Loudness, pitch, and quality are primarily dependent on the characteristics of the airflow that exits the larynx during phonation. This glottal airflow is conditioned by the tracheal air pressure, motion of the vocal folds, approximation of the vocal folds, and the shape of the airways. Efficient vocal control should be revealed though study of voices of people with superior vocal abilities (actors and singers). The way they produce voice, if well understood, should be meaningful also in clarifying concepts of voice therapy. The long range goal of this proposal is to study optimal control and efficiency of the voice through empirical and theoretical studies based on trained and untrained vocalists. The specific goals of this proposal are: (1) to determine the relationships among primary physiologic variables (subglottal pressure, glottal adduction, vocal fold vibratory length, vibrational amplitude) and corresponding acoustic correlates (glottal volume velocity, fundamental frequency, acoustic power) so that a better understanding of vocal efficiency emerges for the trained vocal performer; (2) to determine the aerodynamic, acoustic and kinesthetic parameters that define forward placement, a technique commonly and effectively used in vocal training for voice improvement; (3) to determine the relevance and practical use of vocal tract shaping (vowel modification) to influence the glottal volume velocity waveform and its spectrum relative to loudness and quality control; (4) to determine acoustic and perceptual descriptions of vibrato and tremorous voice; and (5) to refine the computer model SPEAK through use of data from this proposal.